1. Field of the Invention
The present invention relates to a process for the treatment of industrial waste water by electrolysis and, more particularly, for cleaning industrial waste water recovered, for example, from industrial boilers, or otherwise containing contaminants, utilizing an electrocoagulative process to chemically bond with a particle to change the particle from in solution to in suspension which can be flocculated and separated from the water. The invention also relates to an apparatus for carrying out the process and especially to an electrolytic cell and clarifier used for that purpose.
2. Description of the Related Art
The present invention is directed to improving processes and apparatuses for removing impurities from fluids in a manner which is safe, economical, and user friendly. Attempts by others to provide improvements in the art of water purification are represented by the inventions described below.
U.S. Pat. No. 3,849,281 issued to Bennett, et al. discloses a vertically disposed electrolytic cell used to produce hypochlorite solutions. This unit, while impressing a sinuous path upon the fluid to be treated, requires the use of U-shaped plates as a cathode; current is applied only at the outer extremities of the device. This device is divided up into a series of partitioned cell units; it is not constructed so that the individual cell units may be easily cleaned or repaired.
U.S. Pat. No. 4,124,480 issued to Stevenson is directed to a bipolar cell consisting of stacked electrode plates which impresses a sinuous, or partially-sinuous, path upon the electrolytic fluid traveling through it. A partially sinuous path is described when fluid flow stagnation at the ends of the plates is relieved by pathways existing at the ends of certain plates along the path. This cell is used for the electrolytic generation of chlorine from sea water or other brines. The outer plates are both connected to a positive source so as to act as anodes, and the central plate is connected to a negative source to act as a cathode. This device is used for a different purpose than that of the present invention, and is not constructed so as to be particularly easy to disassemble for repair and replacement of interior parts, since each electrode is held in place with a separate O-ring type seal, which must be carefully removed from the cell assembly during inspection to avoid damage, and if damaged, requires replacement.
U.S. Pat. No. 4,339,324 issued to Haas speaks to a gas generator composed of an electrolytic cell which makes use of a series current path and parallel fluid path. Neither the function, nor the structure of this unit is similar to the present invention.
U.S. Pat. Nos. 4,406,768 and 4,500,403 issued to King, disclose other electrochemical cell assemblies; in these units the electrodes do not span the entire width of the inner chamber. However, these units do make use of a series current and parallel fluid paths.
U.S. Pat. No. 5,549,812 issued to Witt, discloses a method of electrolysis which requires a pulsed current flow and sinuous fluid path. A pulsed current source is used to break down and chemically alter contaminants in order to form a flocculate within the fluid to be treated. After treatment, the flocculate is settled in a tank for removal from the fluid. However, the cell is constructed so as to be particularly difficult to disassemble for inspection and repair. Also, the fluid path moves in different directions across each plate within the cell.
U.S. Pat. No. 3,964,991 issued to Sullins, describes an apparatus for electrolytic flocculation (i.e. electrocoagulation) of suspended colloidal particles. This device is cylindrical in form, makes use of a single, centrally-disposed electrode for operation, and is very difficult to disassemble for cleaning after extended use.
German Patent Document DE 3641365C2 is an apparatus for the cleaning and treatment of contaminated water using "electroflotation," a process where iron and aluminum plates, configured as sets of cascaded electrodes, are consumed by electrolysis as waste water passes over them. This electrolytic process (termed herein as "electrocoagulation") can achieve flotation over a wide pH range without the addition of chemicals, resulting in clarification or cleaning of the water. During electroflotation, metals are oxidized in the waste water to form precipitates, emulsions are broken, and oil components are converted to foam. In practice, fine gas bubbles are produced in the waste water (an electrolyte) by electrolytic action between the electrodes, which form anodes and cathodes. Liberated oxygen serves to oxidize substances in the waste water. The release of metallic ions into the waste water provides flocculating agents which cause contaminants to fall to the bottom while gas bubbles may produce a foam bed at the top. A clean water phase forms between the upper foam bed and the heavier dirty component at the bottom of the fluid bed. In this particular apparatus, both iron and aluminum (which is more expensive than iron) are used as sacrificial electrode materials.
As illustrated by the background art efforts are continuously being made to develop improved devices for removing impurities from fluids. No prior effort, however, provides the benefits attendant with the present invention. That is, the process and apparatus according to the present invention substantially depart from conventional concepts and designs of the prior art, and in so doing, provide a means of causing particulate impurities within a fluid to cluster together to form larger particles for filtering by subsequent mechanical processes in an economical manner; provides a cell for electrocoagulation which obviates the need for numerous sealing gaskets, is easy to disassemble and clean, employs readily available parts and materials, is easily manufactured, and uses a minimum number of functional components; and includes a clarifier which is more effective than prior art clarifiers. Additionally, prior patents and commercial techniques do not suggest the present inventive combination of component elements arranged and configured as disclosed and claimed herein.